Traditionally, many components used in the construction or building industry such as cabinets for residential and commercial air handlers and hot air furnaces have been fabricated from sheet metal, and involve a large box-like design that has changed very little over the past several decades. While there are numerous reasons why a molded composite cabinet would present advantages over the traditional metal ones (including a government mandate in regard to SEER rating that manufacturers improve the efficiency of air handling equipment), the industry has not been able to pursue this idea commercially. First, there is significant legislation covering fire and flame spread criteria for the building and construction industry. For example, many jurisdictions require compliance with standard classifications such as Underwriters Laboratory (“UL”) test 723 (also known as 25/50 flame spread/smoke index) when there is more than 10 square feet surface area of non-metallic material utilized in the air flow stream of air conditioning and furnace products having ignition sources. The use of thermoset composite drain pans and blower housings approach in most, and in some instances, exceeds 10 square feet of surface area. Thus, the development of a composite material that complies with UL 723 has long been an unrequited goal of the construction and building industry and its suppliers.
In accordance with the present invention, a composite material is provided that meets this standard (as well as the standards of UBC 8-1, NFPA 225, and ASTM E-84, BS 6853, DIN 5510 and NF F 16-101/102). Moreover, the development of a thermoset composite material that complies with UL 723 provides for significant new products for use in furnace and air conditioning as well as for other construction and transportation applications which require a similar degree of flame and/or smoke spread retardancy. In a further embodiment, the composite material had improved long term stability as it avoids degradation due to microbial activity and may even provide Indoor Air Quality benefits as it may also meet the requirements of one or more of JIS (Japan Industry Standard) Z 2801, ASTM E2180, and ASTM G21.
A second advantage provided by the present invention has to do with sound characteristics. While there are often legislative mandates relating to flame and smoke spread for building and construction applications, there are generally fewer government restrictions relating to noise or sound. It is none-the-less a significant advantage commercially to address these characteristics as the consumer will generally select a product with lower noise emissions. As an example, an air handler or furnace cabinet is often a relatively large hollow box that can actually act to amplify motor sounds, if not sufficiently dampened for sound transmission. Thus, in addition to the government mandated issues relating to fire/flame spread, it is further advantageous if the components help to meet the consumers' demand for quiet home heating and air conditioning. The present invention may also be used to help to improve air quality. The thermoset composite of the present invention helps to further these goals by presenting improved sound dampening ability over the prior art sheet metal components.
Molded polymeric components including for example housings or cabinets or components thereof, present many additional advantages over the prior art metal components. They significantly reduce the potential for injury during assembly by eliminating the need for high temperature welding operations, and for cutting and bending sheet metal. They greatly increase the efficiency of assembly by providing the opportunity for consolidation of components for example, by providing integrally molded functional elements, such as mating elements and/or mounting flanges. Thus, molded polymeric housings have been in use for a significant period of time for blowers for air conditioners, and in particular room air conditioners. In addition, they have been used for small scale heating blowers subjected to relatively low temperatures, such as hair dryers. These applications often involve the use of very expensive compositions, which can be used since the size is small and they are not required to meet the flame spread smoke index retardancy previously discussed. Other hot air furnace components, such as the condensate pan, have been made of molded resins for some time.
However, despite the use of molded polymerics for these other applications and for housings in window air conditioners for well over 30 years, the HVAC industry has failed to capitalize on the many advantages that could be realized through the use of large molded polymeric components for hot air furnaces, air handlers and air conditioning units. There are several reasons to account for the prior art practice, including the belief that the blower environment is better suited for metal, which has proven longevity and noted fire resistance. An additional problem is the lack of understanding in the compounding industry of how to achieve sufficient structural reinforcement, such as through the use of glass fiber reinforcement, while maintaining proper flame and smoke properties for this application. Finally, despite the long recognized advantages and economic incentives, the prior art has failed to produce an acceptable composite material that meets the fire, smoke, and flame spread criteria as set forth in UL 723 Class I and that is moldable in complex shapes with an acceptable appearance.
The present invention provides the solution to the previously mentioned issues, while also presenting a platform for improved efficiencies in the HVAC industry. The present invention provides a molded composite cabinet or cabinet components for hot air furnaces, air handlers and/or air conditioning units. This cabinet may include integral molded functional parts, such as mating elements, and mounting flanges. It has the desired mechanical properties including tensile and impact properties at the necessary operating temperature range. It can be molded into complex configurations and surface characteristics. It does this while maintaining quiet and safe operating conditions.
In addition to the regulations relating to the smoke and flame characteristics of the present invention, there is pending legislation and political posturing regarding the issue of Indoor Air Quality (IAQ). This debate centers around a growing awareness and concern with “sick building syndrome” in which residential and commercial buildings are constructed to conserve energy by sealing the building and relying on central cooling and heating systems to maintain comfortable living temperatures and humidity by re-circulating internal air (and pollutants). Various factors influence the quality of the indoor air, including for example, the supply and quality of the ambient outside air; contamination of indoor air from building materials, carbon monoxide, tobacco smoke, fabric furnishings, carpet adhesives, paint fumes and cleaning products, as well as microbial contamination of ventilation systems or building interiors. The present invention provides an additional method of achieving compliance with existing or proposed regulations by inhibiting or even reducing microbial growth within an HVAC or other construction surface.